We can use more than one generic type in the template function by using the comma to separate the list. We can overload the generic function means that the overloaded template functions can differ in the parameter list. Generic functions perform the same operation for all the versions of a function except the data type differs. From the above example, we overload the ordinary functions. We cannot overload the generic functions as both the functions have different functionalities.
The first one is displaying the value and the second one determines whether the number is even or not. Class Template can also be defined similarly to the Function Template. This helps make template code both flexible and future proof! A function template is a function-like definition that is used to generate one or more overloaded functions, each with a different set of actual types. This is what will allow us to create functions that can work with many different types.
When we create our function template, we use placeholder types also called template types for any parameter types, return types, or types used in the function body that we want to be specified later. Note that we use type int three times in this function: once for parameter x , once for parameter y , and once for the return type of the function.
In this case, because we have only one type that needs replacing int , we only need one template type. And this is still a normal function, not a function template. This is done using what is called a template parameter declaration :. For each template type, we use the keyword typename or class , followed by the name of the template type e. There is no difference between the typename and class keywords in this context.
You will often see people use the class keyword since it was introduced into the language earlier. However, we prefer the newer typename keyword, because it makes it clearer that the template type can be replaced by any type such as a fundamental type , not just class types. We discuss how to create function templates with multiple template types in lesson 8.
Key insight The compiler can use a single template to generate a family of related functions or classes, each using a different set of types. Best practice Use a single capital letter starting with T to name your template types e. Member Message Closed. Templates geoyar 3-Nov I see templates as one of means to auto generate code. You write instructions for the compiler how to generate the code, and the compiler obeys when it sees your order to generate an instantiation of the template.
More to it, you may force the compiler to do some calculation at compile time I mean meta-programming. It seems that you definitely need templates to write libraries, but not in plain apps. Recently, works by Andrei Alexandresku changed or complemented? Re: Templates Sergey Chepurin 3-Nov Frankly speaking, it is easier to write code using templates, especially when you don't care about code bloat. You also can delegate a big portion of your responsibility with most of safety related concerns to compiler isn't that nice?
I think, everyone has something to add to "pros" or "cons" based on his own experience or opinion. That is why i even didn't try to make any conclusion. Meaning this is up to you as a programmer to decide what to choose. Re: Templates geoyar 4-Nov I agree on 'pros' and 'contras', but working with templates is not so easy.
When you are designing a template, you are in parallel designing the classes to be used with the template too to be precise, the concept of the classes. And this asks for a lot more of experience and deep thinking. Add to it template template parameters, non-types, default parameters, typedefs - a lot of things. Definitely, it is not for a beginner. Anyway, thanks for reply. Re: Templates Sergey Chepurin 4-Nov But we can apply a "simple" analogy to a programming process.
This is like designing and building a house - there are even supposed to be windows. And coders are like masons, bricklayers. So, this is a simple part or beginner level in your terminology. To design a project of a house is a job of an architect - class designer with code safety in mind, advanced level in programming terminology. This job always was a difficult one. Now, you can build the house from different materials depending on your wallet, talent, time available, etc.
That is where templates come handy. They are like panels used to construct a buildings from small to skyscrapers. And of course, there is nothing easy in process of building a skyscraper.
Long compilation times Lorenzo Gatti 2-Nov Lorenzo Gatti. Unpleasant compilation times, apart from being justified by pushing computation from run time to compilation time and consequently optimizing much better can usually be disposed of through code organization: confinement of heavyweight templates into separate source files that are not recompiled without need can be achieved through simple idioms like PIMPL.
Re: Long compilation times Sergey Chepurin 2-Nov Now, when processors got to their current limit of power, the parallel computing on multicore platforms and metaprogramming with templates are the techniques experts mostly talk about. But i am afraid that these techniques are so complex that most of us are not ready yet to accept or understand them properly.
This was one of the reasons i have decided to collect at least some of the commonly known and accepted things about templates in this article. For myself - to organize it somehow, and for the others - if they will need it. A couple of comments It's useful to think of templates and classes as being orthogonal rather than competing technologies. Code bloat is not necessarily a consequence of template explansion. Dimensional analysis and other iterative aspects of algorithms can occur at compile time hence the loooooong builds.
Type safety is a key advantage of generic code, but also a source of many incomprehensible compiler messages. Liberal use of const a good thing is often abandoned a bad thing in the face of hard to compile generic code. Poor compiler support for templates eg, incomprehensible messages is mainly due to the relative immaturity of the technology.. You say "Templates are sometimes a better solution than C macros and void pointers".
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